Transceiving With a Predetermined Frequency Spacing

Abstract

An apparatus comprises: a receiver; a transmitter; a laser device coupled to the receiver and the transmitter and comprising: a first laser configured to provide to the receiver a first optical wave centered at a first frequency, and a second laser configured to provide to the transmitter a second optical wave centered at a second frequency, the first frequency and the second frequency have a predetermined frequency spacing; and a processor coupled to the receiver, the transmitter, and the laser device, with the processor configured to control the first laser and the second laser to maintain the predetermined frequency spacing.

What is claimed is: 
     
         1 . An apparatus comprising:
 a receiver;   a transmitter;   a laser device coupled to the receiver and the transmitter and comprising:
 a first laser configured to provide to the receiver a first optical wave centered at a first frequency, and 
 a second laser configured to provide to the transmitter a second optical wave centered at a second frequency, the first frequency and the second frequency have a predetermined frequency spacing; and 
   a processor coupled to the receiver, the transmitter, and the laser device and configured to control the first laser and the second laser to maintain the predetermined frequency spacing.   
     
     
         2 . The apparatus of  claim 1 , wherein the first laser is a local oscillator (LO), and wherein the first optical wave is an LO wave, and wherein the receiver is a coherent optical receiver configured to:
 receive a downstream optical signal centered at a third frequency;   receive the LO wave from the first laser;   determine a frequency offset between the first frequency and the third frequency; and   provide to the processor a feedback signal based on the frequency offset.   
     
     
         3 . The apparatus of  claim 1 , wherein the second laser is a carrier laser, and wherein the second optical wave is a carrier wave, and wherein the transmitter is configured to:
 receive the carrier wave from the second laser;   receive a data signal from the processor;   modulate the carrier wave using the data signal to create an upstream optical signal; and   provide the upstream optical signal.   
     
     
         4 . The apparatus of  claim 3 , wherein the transmitter is further configured to further modulate the carrier wave using on-off keying (OOK) modulation or pulse-amplitude modulation (PAM). 
     
     
         5 . The apparatus of  claim 1 , further comprising:
 a splitter coupled to the receiver and the transmitter and configured to:
 provide a downstream optical signal to the receiver, and 
 receive an upstream optical signal from the transmitter; and 
   a port coupled to the splitter and configured to:
 receive the downstream optical signal from a second apparatus over an optical fiber, 
 provide the downstream optical signal to the splitter, 
 receive the upstream optical signal from the splitter, and 
 transmit the upstream optical signal towards the second apparatus over the optical fiber. 
   
     
     
         6 . The apparatus of  claim 5 , wherein the port is further configured to provide bidirectional communication over the optical fiber, and wherein the port is the only communications port in the apparatus. 
     
     
         7 . The apparatus of  claim 1 , wherein the laser device further comprises a controller coupled to the processor and configured to:
 receive a control signal from the processor; and   perform a control action on both the first laser and the second laser in response to the control signal,   wherein the controller is a heater and the control action is heating, the controller is a thermoelectric cooler (TEC) and the control action is cooling, or the controller is a bias current controller and the control action is a bias current.   
     
     
         8 . The apparatus of  claim 1 , wherein the predetermined frequency spacing is set by a design of the laser device, wherein the processor is further configured to further maintain the predetermined frequency spacing independent of an ambient temperature, and wherein the predetermined frequency spacing is about 100 gigahertz (GHz). 
     
     
         9 . The apparatus of  claim 1 , wherein the apparatus is an optical network unit (ONU) in a point-to-multipoint (PTMP) network. 
     
     
         10 . A method comprising:
 providing, by a first laser of a laser device and to a receiver, a first optical wave centered at a first frequency;   providing, by a second laser of the laser device and to a transmitter, a second optical wave centered at a second frequency, the first frequency and the second frequency have a predetermined frequency spacing; and   maintaining, by a processor coupled to the laser device, the predetermined frequency spacing.   
     
     
         11 . The method of  claim 10 , further comprising:
 receiving a downstream optical signal centered at a third frequency;   determining a frequency offset between the first frequency and the third frequency; and   providing to the processor a feedback signal based on the frequency offset.   
     
     
         12 . The method of  claim 10 , wherein the second optical wave is a carrier wave, and wherein the method further comprises:
 receiving a data signal from the processor; and   modulating the carrier wave using the data signal to create an upstream optical signal.   
     
     
         13 . The method of  claim 10 , further comprising:
 receiving a control signal from the processor; and   performing a control action on both the first laser and the second laser in response to the control signal.   
     
     
         14 . The method of  claim 13 , wherein the control action is heating, cooling, or a bias current. 
     
     
         15 . The method of  claim 10 , further comprising further maintaining the predetermined frequency spacing independent of an ambient temperature. 
     
     
         16 . An optical network unit (ONU) comprising:
 a receiver;   a laser device coupled to the receiver and comprising:
 a first laser configured to provide to the receiver a first optical wave centered at a first frequency, and 
 a second laser configured to provide an upstream optical signal centered at a second frequency, the first frequency and the second frequency have a predetermined frequency spacing, and the second laser is a directly-modulated laser (DML); and 
   a processor coupled to the receiver and the laser device and configured to control the first laser and the second laser to maintain the predetermined frequency spacing.   
     
     
         17 . The ONU of  claim 16 , wherein the first laser is a local oscillator (LO), wherein the first optical wave is an LO wave, and wherein the receiver is configured to:
 receive a downstream optical signal centered at a third frequency;   receive the LO wave from the first laser;   determine a frequency offset between the first frequency and the third frequency; and   provide to the processor a feedback signal based on the frequency offset.   
     
     
         18 . The ONU of any of  claim 16 , further comprising a splitter coupled to the receiver and the second laser and configured to:
 provide a downstream optical signal to the receiver; and   receive the upstream optical signal from the second laser.   
     
     
         19 . The ONU of  claim 18 , further comprising a port coupled to the splitter and configured to:
 receive the downstream optical signal from an optical line terminal (OLT) over an optical fiber,   provide the downstream optical signal to the splitter,   receive the upstream optical signal from the splitter, and   transmit the upstream optical signal towards the OLT over the optical fiber.   
     
     
         20 . The ONU of  claim 16 , wherein the laser device further comprises a controller coupled to the processor and configured to:
 receive a control signal from the processor; and   
       perform a control action on both the first laser and the second laser in response to the control signal.